Prepare Oven and Pan: Adjust an oven rack to the middle position and set your oven to preheat at 425 degrees F (approximately 220 degrees C). Line a large baking sheet with parchment paper for easier cleanup, if desired.
Season Shrimp and Colorful Vegetables: In a large mixing bowl, combine the prepared shrimp, sliced red and yellow bell peppers, and sliced red onion. Sprinkle with the chili powder, garlic powder, onion powder, ground cumin, smoked paprika, and black pepper. Add 3 of the minced garlic cloves (half of the total), 2 1/4 tablespoons (half) of the olive oil, and 3/4 teaspoon (half) of the salt. Toss everything together thoroughly to ensure all components are evenly coated with the oil and seasonings.
Arrange on Baking Sheet (Part 1): Carefully distribute the seasoned shrimp and vegetable mixture in a single, even layer across approximately two-thirds of your prepared baking sheet. Avoid overcrowding to ensure proper roasting.
Prepare Zucchini Noodles: To the same mixing bowl (no need to wash), add the zucchini noodles. Drizzle with the remaining 2 1/4 tablespoons of olive oil, the remaining 3 minced garlic cloves, the remaining 3/4 teaspoon of salt, and the dried oregano. Gently toss the zucchini noodles to coat them well.
Arrange on Baking Sheet (Part 2): Neatly place the seasoned zucchini noodles onto the remaining one-third of the baking sheet, keeping them somewhat separate from the shrimp and pepper mixture.
Roast to Perfection: Transfer the baking sheet to the preheated oven. Roast for 12-15 minutes. The shrimp should be pink, opaque, and cooked through, and the vegetables should be tender-crisp with slight caramelization.
Serve Immediately: Carefully remove the baking sheet from the oven. To serve, create a bed of the warm zucchini noodles on each individual plate and then top generously with the roasted shrimp and colorful vegetable medley. This dish is best enjoyed hot.